The organisation charged with saving Gaelic from extinction has admitted it will fail to achieve one of its key targets.

Two years ago Bòrd na Gàidhlig (BnG), the principal public body promoting and developing Gaelic, committed itself to 1600 adult learners completing a new Gaelic course by the end of next month.

It now says that cannot be achieved. It does not yet know what the final figure will be, but The Herald has established that in the Highland Council area, where around 200 people were following the course, only about a dozen have completed it.

Although it has achieved its goal of 2000 adults taking up the Ulpan method of Gaelic learning, a spokesman for BnG confirmed it would miss the target it set for March 31, despite giving out funding of £250,000 for courses to be developed in this financial year alone.

The BnG spokesman said: "Bòrd na Gàidhlig is pleased that nearly 2000 more adults are learning Gaelic through the Ùlpan method in line with the targets ... but acknowledges that the original target for the numbers completing all the Ùlpan units has proved, in the light of experience, to be unrealistic."

In April 2010, BnG, which was set up by the Gaelic Language Act in 2005, published "Ginealach Ùr na Gàidhlig" – an action plan to increase the numbers of Gaelic speakers.

It proposed to accelerate the number of people learning and using Gaelic and ensure the most effective use of existing resources and structures between 2010 and this year.

As well as long-established courses, it promoted the use of a fast-track method, originally devised to teach Hebrew to immigrants to Israel.

The Ùlpan method, which is also used to teach Welsh, has a reputation as a quick and effective way for adults to become fluent in a language.

It has been used to teach more than a million immigrants to Israel since the 1940s, with repetition of vocabulary a keystone.

A company, Deiseal Ltd, was set up to deliver Ùlpan courses and in this current financial year BnG has given it a grant of £250,000 to roll out and develop Ùlpan courses.

BnG now says that 1917 students are registered with over 150 accredited tutors nationwide, meaning it will likely achieve its target of having 2000 adults learning Gaelic by March 31.

But the second target, of an 80% completion rate, has proved too ambitious.

The BnG spokesman said the targets had been based on an immediate start and completion in the timescale set out by Deiseal, but it had taken longer than thought to secure funding from sources other than BnG.

He said: "While it is possible to complete all the Ùlpan units in around six weeks of intensive immersion, covering 24 units per week, the delivery of the courses has to fit in with the needs of the clients.

"Immersion over short, intensive periods has been available in some areas but circumstances dictate that many students are undertaking classes in evenings, or in lunch breaks, which means it will take them longer to reach completion."

One student of the language, who wished to remain anonymous, was critical of the Ùlpan method.

He told The Herald: "Ùlpan is educationally flawed, being neither thematic, structured, nor logical in its development of language and based on a false premise of auditory learning,"

He said this was fine for very young children or for adults learning a majority language such as Hebrew in Israel: "In both these cases the learners are continually surrounded by the sounds of the spoken language, but that's rare for Gaelic."

Christine Matheson, a librarian at Drumnadrochit on Loch Ness, disputed that view.

She said: "I have done 90 of the 144 units across almost two -and-a-half years and am very impressed."